In the manufacture of tungsten wire for lamp filaments and the like, the tungsten is reduced through various processes from billet size to thin filament wire. The process generally includes rough swaging to reduce the billet to rod form and then more precision swaging to reduce the rod to a diameter small enough to be drawn on wire drawing machines to reduce the subsequent wire diameter to that required for the manufacture of lamp filaments. During the intermediate continuous rod swaging process, the rods are moving axially as well as rotating through the swaging machine which creates significant vibrations in the rod as it feeds toward the swaging machine. It is desirous at this point in the manufacturing process to sense and measure cracks and surface defects in the tungsten rod, which cracks and defects can have a significant effect on the quality of the finished tungsten wire. Commercial equipment for sensing the surface defects and cracks include an electromechanical coil through which the rod must axially pass and the efficiency and accuracy of commercial defect sensing equipment can be severely impaired when the rod is vibrating. Elimination, or at least the substantial dampenin of these vibrations in the rod is accordingly critical to the accurate sensing of surface cracks and defects in the rod just prior to its entering the swaging machine.
Since axial movement as well as continuous rotating movement of the rod is essential to the swaging process any mechanism for dampening the vibrations in the rod as it passes through the defect sensing device must allow for the free axial as well as rotational movement of the rod without any impairment of that motion by the dampening device.